The detrimental effects of exposing the skin to UV-light are manifold and are well documented in the prior art. In particular, it is well known that UV-B radiation (wavelength of about 290 to about 315 nm) causes erythematic disorders or sunburn whereas UV-A radiation (wavelength from about 315 to about 400 nm) causes phototoxic and photochemical reactions.
The use of organic UV-absorbing compounds for sunscreen applications is also widely known. A disadvantage of organic UV-absorbing compounds is their low water solubility. Hydrophobic UV-absorbing compounds, with or without the combination with organic solvents, are capable of passing the so-called stratum corneum with the risk of entering the bloodstream.
A further disadvantage of many organic UV-absorbing compounds is that they are unstable under UV-light and prone to degradation. UV-exposure can cause photochemical reactions that destroy the UV-absorbing compound thereby reducing the protection against UV radiation in time.
U.S. Pat. No. 4,045,229 discloses photographic elements comprising a support, a radiation sensitive silver halide emulsion layer and a UV-absorbing 1-amino-4-cyano-1,3-butadiene compound.
U.S. Pat. No. 4,839,160 discloses a cosmetic formulation for protecting the skin against UV-radiation comprising a UV-absorbing polymer of benzylidenenobornanone units having C4-C12 alkoxy chains.
UV-A and UV-B absorbing compounds coupled through an oxygen or nitrogen atom to a polyacrylic backbone are known from WO 2001/08647. These products are substantially insoluble particles and are formulated with a carrier into sunscreen compositions, said carrier being capable of being absorbed by the substantially insoluble particles, altering the refractive index of the sunscreen composition and rendering the sunscreen composition essentially transparent to the skin. As a carrier, oily (i.e. strongly hydrophobic) components such as tocopherol or a functional analogue or derivative thereof, a vegetable oil, a mineral oil or a silicone oil, is used which enhances the risk of skin penetration.
WO 2000/065142 discloses polymers with broad UV-absorption for protection of textile materials against UV-radiation by adhering these polymers to textile fibres. However, WO 2000/065142 is silent with respect to sunscreen compositions.
FR A 2.757.389 discloses the combined use of UV-absorbing compounds and a hyperbranched or dendrimeric polymer in sunscreen formulations.
WO 2004/006878 discloses merocyanine derivatives for cosmetic use, in particular sunscreen formulations.
WO 2004/075871 discloses cosmetic compositions for protection against UV-A-radiation comprising for example a product obtained by coupling aminobutadienes and a polymer having free amino groups.
WO 2005/058269 discloses merocyanine compounds as UV-A absorbers. These compounds can be used both in dissolved form and in the micronized state.
WO 2006/003094 discloses merocyanine derivatives and oligomers thereof for protecting human hair and skin against the damaging effect of UV-A-radiation.
WO 2006/009451 discloses dendrimer-aminobutadiene-based UV-A-protecting products.
WO 2006/032741 discloses silane merocyanine sulphone derivatives, compositions comprising such silane merocyanine sulphone derivatives and the use of these compositions as UV protecting products.
WO 2006/125676 discloses a method for improving the photochemical stability of UV-A protecting dibenzoylmethane compounds by combining these with a merocyanine sulphone derivative and compositions comprising a UV-A-protecting dibenzoylmethane compound and a merocyanine sulphone derivative.
EP 1.728.501 A1 discloses a cosmetic preparation comprising at least an UV-A-light protection filter, which is bound to a polypeptide, at least an UV-B-light protection filter and/or a broadband filter.
WO 2006/016806 discloses the use of UV-A-absorbing compounds in cosmetic compositions.
WO 2007/014848 discloses the use of merocyanine derivatives and oligomers thereof for protecting body-care and household products from photolytic and oxidative degradation.
WO 2007/071582 discloses the use of merocyanine derivatives for protecting body-care and household products against the harmful effect of UV-radiation.
In spite of these attempts, there remains a need for UV-absorbing components which provide sufficient direct protection against sunlight by absorbing UV-radiation while not showing substantial penetration through the skin. There is also a need for UV-absorbing components that are substantially transparent for visible light radiation. In addition, there is a need for UV-absorbing components that are heat and UV-light stable and which are well soluble or dispersable in ingredients used in cosmetic compositions.